Air jet gyro drift control



July 13, 1943. R, M HENTZ 2,324,157

AIR JET GYRO DRIFT CONTROL Filed Feb. 5, 1942 Fig.1

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INVENTOR. 1 41P M fiv/vrz ATTOK/Vfl Patented July 13, 1943 UNITED STATESPATENT OFFICE AIR JET GYRO DRIFT CONTROL Ralph M. Heintz, Cleveland,Ohio, assignor to Jack & Heintz, Inc., Cleveland, Ohio 2 Claims.

This invention relates to improvements in directional gyroscopes and hasparticular reference to means for preventing the drift of the gyroscopeaway from a set course or azimuth posi tion.

While a gyroscope will theoretically maintain any fixed orientation inspace after being set in such position it is found in practice thatthere is invariably a tendency to slowly creep or drift away from theset position. The factors contributing to produce this undesirableeffect may all be summed up as resulting from physical limitations andimperfections which cannot be eliminated regardless of the skill andprecision employed in the manufacture of the instrument.

It is an object of the present invention to provide means for preventingthis drift, to thereby maintain the gyroscope in its true orientationwithout the necessity for very frequent readjustment or resetting,

A specific object of the invention is to provide an air jet control toprevent drift of the directional element of a gyroscope on a vehiclewhile travelling on a predetermined course.

In connection with the following description reference will be made tothe attached drawing forming a part of this specification, in which:

Figure 1 is a vertical sectional view through a directional gyroscopeembodying the novel features of the present invention, and

Figure 2 is an enlarged fragmentary View taken on the line 2--2 of Fig.1.

The gyroscope to which th invention is applied includes in general theusual components of a conventional directional gyroscope. A rotatablecircular frame carries a scale or card 2 oriented by means of the gearteeth 3. A gimbal ring 4 is supported in vertical bearings 5 and 6, andsupports in bearings 1 and 8 a rotor frame 9 carrying an air drivenrotor NJ. The gimbal frame 4 carries the conventional compass card llarranged for rotation adjacent the relatively fixed scale or card 2 onthe circular frame I,

In the illustrated embodiment the air supply for driving the rotor isadmitted through a cham ber 28 and passage 29 to an annular chamber 30surrounding the lower shaft or trunnion 3| of the gimbal frame 4.Lateral passages 32 and an axial passage 33 convey the air to a hollowmember 34 provided with a nozzle 35 for delivering a jet or jets of airinto the buckets of the rotor I0 according to conventional practice.

The present invention involves the use of an auxiliary nozzle carried bythe gimbal frame 4 for directing air jets against relatively stationaryvanes in such a. manner as to resiliently maintain the auxiliary nozzleand gimbal frame in a fixed position with respect to said vanes, whichposition is established and maintained by the application of arelatively small force suflicient to resist the tendency to drift. Foraccomplishing this additional function the hollow member 34 is providedwith an extension tube 36 terminating in a pair of divergent, upwardlydirected nozzles 3'1 and 38. In the present construction the gimhalframe 4 is provided with an opening at 39 for the passage of the tubularextension 36. The rotatable frame carries a pair of vanes 48 and 4| justabove the nozzles 3'! and 38 and appropriately spaced to intercept airjets 43 and 44 from said nozzles when the extension 36 is centeredbetween the vanes. The vanes 40 and 4| are positioned on the rotatableframe I so that they will be equally spaced from the respective nozzles31 and 38, as shown in Fig. 2, when the cards 2 and H are in zero-zeroalignment.

When an air pressure differential has been established in the system,air jets will issue from the nozzles 35, 31 and 38. The jet from the.-nozzle 35 drives the rotor l0, and the jets 43 and. 44 from the nozzles31 and 38 impinge upon the vanes 40 and 4|. When the circular frame Iis. set to on course position, or in zero-zero relation with the card I,the reactions of the air jets- 43 and 44 upon the extension 36 tend toresist movement of the nozzles 31 and 38 with respect to the vanes 40and 4| and thereby exert light forces to prevent drift of thedirectional components of the gyroscope with respect to the frame I andthe card 2. The design of the nozzles 31 and 38 and their arrangementwith respect to the vanes 46 and 4| is such, however, that the forcesexerted by these elements are relatively slight with respect to thegyroscopic forces produced in the instrument so that the producing ofnormal directional indications is not interfered with. The card istherefore free for rotation by the directional forces of the gyroscopebut at the same time it is lightly and resiliently constrained withsufficient force to prevent its drifting away from its set position whenthe vehicle and the frame I are on course.

Ordinarily, navigation by a gyroscopic compass or the like involves themaintaining of a set course for considerable periods of time. Duringthese periods the drift control of the present invention will beeffective to prevent drift of the gyroscope. The time required forchange of course or other turns is relatively short and the amount ofdrift occurring during such a turn would ordinarily be negligible.

It is of course understood that the air flow through the variouspassages and nozzles just described is produced by maintaining apressure difference between the source of air supply communicating withthe chamber 28 and the interior of a sealed casing or box 42 surroundingthe instrument. For the purpose of the present invention it isimmaterial Whether this pressure difference be established by openingthe chamber 28 to the atmosphere and exhausting the box 32, or bypumping air under pressure into the chamber 28 so as to pass out throughthe nozzles 35, 3'! and 38.

It is to be understood that only a single preferred embodiment of theinvention has been described herein for purposes or illustration butthat the invention is capable of many modifications. Changes in theconstruction and arrangement of parts may be made which do not departfrom the spirit and scope of the appended claims.

I claim:

1. In a directional gyroscope for aircraft, a frame member rotatable ona normally vertical axis, said frame member carrying an azimuthreference scale and being adapted to be turned to a selected fixedposition with respect to said aircraft, a directional element comprisinga vertical gimbal ring rotatable about said axis, an

. 30 azimuth scale on said directional element adj acent said referencescale, a rotor bearing frame pivot ally carried in said gimbal ring,upwardly directed air jet nozzle means carried by said gimbal ring,- andvane means on said frame member adapted to cooperate with said nozzlemeans to resiliently maintain said gimbal ring in a predeterminedorientation with respect to said frame member when air is flowingthrough said nozzle means, to prevent drifting of said directionalelement.

2. In a directional gyroscope for aircraft, a frame member rotatable ona normally vertical axis, said frame member carrying an azimuthreference scale and being adapted to be turned to a selected fixedposition with respect to said aircraft, a directional element comprisinga vertical gimbal ring rotatable about said axis, an azimuth scale onsaid directional element adjacent said reference scale, a rotor bearingframe pivotally carried in said gimbal ring, a unitary hollow membercarried in said gimbal ring, a rotor driving nozzle on said hollowmember, a pair of divergent nozzles on said hollow member adjacent saidframe member, and a pair of vanes on said frame member arranged tointercept air jets from said divergent nozzles to resiliently maintainsaid gimbal ring in a predetermined orientation with respect to saidframe member when air is flowing through said nozzles, to preventdrifting of said directional element.

RALPH M. HEINTZ.

